Glaucoma is an ocular disease complex associated with an elevated pressure within the eye (i.e., intraocular pressure, IOP). As a result of the elevated IOP, damage to the optic nerve resulting in irreversible loss of visual function may ensue. Untreated, this condition may eventually lead to blindness.
Ocular hypertension, i.e., the condition of elevated intraocular pressure without optic nerve damage or characteristic glaucomatous visual field loss, is now believed by the majority of ophthalmologists to represent the earliest phase in the onset of glaucoma.
A number of the drugs presently employed to treat glaucoma are not entirely satisfactory, particularly in the earliest course of the disease when the side effects they produce are often worse than the symptoms of the disease.
Epinephrine, used as a topical solution, must be utilized cautiously in patients with high blood pressure, diabetes, hyperthyroidism and cerebral artereosclerosis due to the possibility of systemic action.
Timolol, a clinically utilized, topically applied agent for lowering intraocular pressure, must be used with caution in patients in whom beta-adrenergic blockade may be undesirable. Systemic absorption of topically administered timolol and systemic beta-blockade are responsible for the contraindication of timolol therapy for glaucoma in patients with compromised pulmonary function and in patients who cannot tolerate its systemic cardiovascular action.
Pilocarpine, a topical drug, although considered systemically harmless and quite effective, may cause considerable local difficulties. Pupillary constriction causes the eye to lose its ability to adapt from light to dark. Accommodation may become stimulated so that the patient's refraction is sometimes incorrect and vision becomes blurred. The drug itself may cause a local vasodilation and red eyes. Irritation is common.
Carbonic anhydrase inhibitors have been used systemically but they have a number of disadvantages. While effective in lowering intraocular pressure, they often cause a numbness and tingling, gastrointestinal upsets and, frequently, depression, lethargy, a loss of appetite, and general malaise. European Patent Application 81400326.5, Publication number 36,351 attempts to overcome these difficulties by the topical administration of an alkali metal salt of a carbonic anhydrase inhibitor.
The present invention provides a new composition and method for reducing and controlling elevated intraocular pressure, especially the elevated IOP associated with glaucoma.